media: dvb: Fix secure demux application load check

To deduce whether secure demux is available, an attempt is made to
load the secure demux appliction during module initialization.
The loading process retrieves the application from filesystem.
When kernel configuration is set so that the module is built-in
as part of the kernel image, filesystem is not yet available
and loading fails.
This change moves the loading attempt from initialization
to first usage of status query, which occurs after device
is opened by user-space and filesystem is sure to be available.

Change-Id: I22d24054196f6068bf28e2ba6f2a4da6a9340730
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>